Throw out what you've been told about parking yourself cross-legged for twenty minutes and aiming for a "blank mind." That sentence alone was dreamed up by someone whose brain has only a handful of tabs open at once, https://themindfulcounselor.me/blog/meditation-myths.
The ADHD brain thrives on dopamine and novelty, and a stream of sensory information, so the opposite of those things (stillness, quiet, repetition) when demanded of us, would in most people cause them to feel inadequate, like everyone else would; but also feel like a massive letdown. Which, again, does never really come from willpower — it comes from using it the wrong way. Start with two minutes.
Don't reach for ten minutes.
Actually start trying for two; which, in the first 30 seconds of which, you are going to wander away in some kind of awesome way anyway; so with all due respect, the less runway you have when it first bolts, the less time it has to gain momentum,and you can reel it in! Success is simply coming back,and this is your entire rep. Doing the rep for 50 occasions throughout two minutes,you would most certainly generate a stronger attention muscle than someone who just sat quietly for twenty minutes on the floor —totally aware of absolutely nothing.
Movement works wonders; meditative walking, moving to music, even walking laps around the room; or literally any physical activity while attempting meditation... Anything! Consider pacing the house or the room with something to hold or touch and just pay attention to your breathing when it isn't a good situation at all —if anyone in the world were to witness your behavior! Whether you buy it or not... "tidy up the kitchen" meditation (running water, hands occupied and mind in its body) is often times how the most present and intelligent minds genuinely find calm with meditation instead of a perfectly poised, yoga-poster like, meditative bliss pose.
Audio can be another savior where true silence becomes nearly intolerable in an ADHD brain. Put on your favorite meditation recordings, background tones, or even just a ticking clock in your room and your brain will take care of the rest by locking onto whatever thing it is listening to!
Placement of this meditation session within your daily schedule matters too... If you take prescription medication that you take at some point daily then this is typically a much better time than early morning, when your brain is nowhere near ready.